Coupler Structures for the LHC Beam Pipe Reflectometer

The LHC reflectometer will be used to detect and locate obstacles and other kinds of discontinuities in the LHC beam screen. An important part of the system is the RF coupler element, which provides the interface between the beam pipe and the measurement equipment. A very careful design of those coupler structures is necessary since the coupler's properties are expected to have a large impact on the overall system performance. Two different options for the reflectometer operation are considered: Measurements over 200m during LHC assembly and in-situ measurements after completion over half a cold arc. Various coupling structures are discussed for both options.